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Subject[PATCH] modpost: Copy namespace string into 'struct symbol'
Date
When building an out-of-tree module I was receiving many warnings from
modpost like:

WARNING: module dahdi_vpmadt032_loader uses symbol __kmalloc from namespace ts/dahdi-linux/drivers/dahdi/dahdi-version.o: ..., but does not import it.
WARNING: module dahdi_vpmadt032_loader uses symbol vpmadtreg_register from namespace linux/drivers/dahdi/dahdi-version.o: ..., but does not import it.
WARNING: module dahdi_vpmadt032_loader uses symbol param_ops_int from namespace ahdi-linux/drivers/dahdi/dahdi-version.o: ..., but does not import it.
WARNING: module dahdi_vpmadt032_loader uses symbol __init_waitqueue_head from namespace ux/drivers/dahdi/dahdi-version.o: ..., but does not import it.
...

The fundamental issue appears to be that read_dump() is passing a
pointer to a statically allocated buffer for the namespace which is
reused as the file is parsed.

This change makes it so that 'struct symbol' holds a copy of the
namespace string in the same way that it holds a copy of the symbol
string. Because a copy is being made, handle_modversion can now free the
temporary copy

Fixes: cb9b55d21fe0 ("modpost: add support for symbol namespaces")
Cc: Martijn Coenen <maco@android.com>
Cc: Joel Fernandes (Google) <joel@joelfernandes.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Matthias Maennich <maennich@google.com>
Cc: Jessica Yu <jeyu@kernel.org>
Signed-off-by: Shaun Ruffell <sruffell@sruffell.net>
---

Hi,

I didn't test that this change works with the namespaces, or investigate why
read_dump() is only called first while building out-of-tree modules, but it does
seem correct to me for the symbol to own the memory backing the namespace
string.

I also realize I'm jumping the gun a bit by testing against master before
5.4-rc1 is tagged.

Shaun

scripts/mod/modpost.c | 31 +++++++++++++++++++++++++++++--
1 file changed, 29 insertions(+), 2 deletions(-)

diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index 3961941e8e7a..349832ead200 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -364,6 +364,24 @@ static const char *sym_extract_namespace(const char **symname)
return NULL;
}

+static const char *dup_namespace(const char *namespace)
+{
+ if (!namespace || (namespace[0] == '\0'))
+ return NULL;
+ return NOFAIL(strdup(namespace));
+}
+
+static bool is_equal(const char *n1, const char *n2)
+{
+ if (n1 && !n2)
+ return false;
+ if (!n1 && n2)
+ return false;
+ if (!n1 && !n2)
+ return true;
+ return strcmp(n1, n2) == 0;
+}
+
/**
* Add an exported symbol - it may have already been added without a
* CRC, in this case just update the CRC
@@ -375,7 +393,7 @@ static struct symbol *sym_add_exported(const char *name, const char *namespace,

if (!s) {
s = new_symbol(name, mod, export);
- s->namespace = namespace;
+ s->namespace = dup_namespace(namespace);
} else {
if (!s->preloaded) {
warn("%s: '%s' exported twice. Previous export was in %s%s\n",
@@ -384,6 +402,12 @@ static struct symbol *sym_add_exported(const char *name, const char *namespace,
} else {
/* In case Module.symvers was out of date */
s->module = mod;
+
+ /* In case the namespace was out of date */
+ if (!is_equal(s->namespace, namespace)) {
+ free((char *)s->namespace);
+ s->namespace = dup_namespace(namespace);
+ }
}
}
s->preloaded = 0;
@@ -672,7 +696,6 @@ static void handle_modversions(struct module *mod, struct elf_info *info,
unsigned int crc;
enum export export;
bool is_crc = false;
- const char *name, *namespace;

if ((!is_vmlinux(mod->name) || mod->is_dot_o) &&
strstarts(symname, "__ksymtab"))
@@ -744,9 +767,13 @@ static void handle_modversions(struct module *mod, struct elf_info *info,
default:
/* All exported symbols */
if (strstarts(symname, "__ksymtab_")) {
+ const char *name, *namespace;
+
name = symname + strlen("__ksymtab_");
namespace = sym_extract_namespace(&name);
sym_add_exported(name, namespace, mod, export);
+ if (namespace)
+ free((char *)name);
}
if (strcmp(symname, "init_module") == 0)
mod->has_init = 1;
--
2.17.1
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